Apparatus for bending and drawing sheet metal.



N. A. ROBERTSON.

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N. A. ROBERTSON.

APPARATUS FOR BENDING AND DRAWING SHEET METAL.

APPLICATIONI'ILHDSBP'LQS,1915!.

1,078,959 Patented Nov. 18, 1913. ,Z "zlq: 4.

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N. A. ROBERTSON. APPARATUS FOR. BENDING AND DRAWING SHEET METAL. APPLICATION FILED SEPT. 23, 1912.

1,078,959, Patented N0v.18, 1913.

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NORMAN A. ROBERTSON, on new YORK, N. Y.

APPARATUS FOR IBENDING AND DRAWING SHEET METAL.

Specification of Letters Patent.

Patented Nov. 18, 1913.

Original applicationfiled May 8, 1912, Serial No. 695,881. Divided and this application filed September 23, 1912. Serial No. 721,957.

a specification.

This application is a division of my application No. 695,881, filed May 8, 1912, describing a method and apparatus for bending and drawing sheet metal, such for ex ample as iron or steel or aluminum, and especially for drawing the irregularlyshaped parts of the bodies of automobiles and similar vehicles; the present applica tion being limited to the apparatus.

Automobile bodies usually comprise a supporting floor, and sides and ends which The sides and ends have been'made of plates of metal some or all of which are bent both in a longitudinal and in a transverse direction so as to pro duce convenient and graceful shapes. Except at the cornersbetwcen the sides and the ends the curvature of the plates has been comparatively slight, and it has been the practice heretofore to shape the plates by hand, at a very considerable expense. This invention provides'for the drawing of the plates into the desired shape entirely by machinery, thus securing greater accuracy and economy than can be secured by hand Work. 4

In the accompanying 'drawings,-Figures 1,-2' and 3 are respectively an elevation, inverted plan, and section (onthe line 3-3 of Fig. 1) of a plate adapted to form the rear end of an automobile body; Figs. 4., 5, 6 and 7 illustrate a suitable embodiment of this invention for making the end plate of Figs. 1, 2 and 3, Fig. 4: being a front elevation,'partly in section, Fig. 5 being a horizontal section on the line of Fig. 4, Fig. 6 a central transverse section, and Fig. 7 an end elevation.

The article shown in Figs. 1, 2 and is an unfinished end plate or seat back andis selected as typical of the numerous diil'erent shapes which can be made according to the principles of this invention. Calling the distance from right to left in the drawing the length of the sheet, Fig. 2 shows that it is curved longitudinally to form the center A.

' therein.

and the end portions B at approximately a right angle to the central portion; and Fig.

3 shows that the central ortion is curved transversely, the curve being 01 slight degree and being of reversed or S-shape. Ad-

'jaccnt to the upperand lower edges of the plates are stiffening ribs C and D stamped Similar intermediate ribs F are formed in the back or central portion. The ends of the'plate are unfinished, being subsequently trimmed and bent in any usual or suitable press. In shaping the plate, the blank is held at two opposite sides, and left free at the other two sides. For example,

"for making the plate of Fig. 1 it would be held only at the end portions 13. Notwithstanding that the blank is free at thetop and bottom sides, it is drawn into a shape which iscurved in the transverse direction as well as in the longitudinal direction, the holding of the ends being sulliclent to permit the limited amount 01 transverse shaping required. It is ossiblc in fact to secure most of the shapes (1 esircd by the mere pressure of the shaping punch upon one face of the sheet, without the necessity ofan opposing die, the desired shape being obtained by the mere stretching of the metal over the punch by reason of the relative movement between the punch and the clamped ends of the blank.

In the machine illustrated a pair of blank holders or grippers G are located at each side of the machine, being removably mounted on blocks 11 which are mounted, one at each side of the machine, on the upper ends .of a pair of plungers H which work in hydraulic cylinders J; the blocks 11 at oppositc sides being connected to each other by means of cross bars K, and the cylinders ;J being mounted on a cross-head or platen L on the top of the plunger M of the main .ram by which the punch N is raised and lowered. The upper die O is fixed in the upper press head 0 and carries removable grippers P. The upper grippers P and the lower grippers G are made detachable, so that grippers of different shapes maybe put into the machine for making plates having dill'erently shaped ends.

The cylinders J are connected to any usual or suitable type of accumulators whereby a constant hydraulic pressure is maintained on the plunger-s H, this pressure being calculated to permit a drawing of the sheet Q, through the grippers with considerable friction as the punch advances, and being adjustable to different pressures. The punch N is mounted on a frame R which is provided with projecting lugs S Which engage the upper edges of the tie bars K so as .to hold the grippers G away from the blank until the punch commences to advance; after which the blank is gripped with a constant pressure during the entire drawing operation, the lugs S rising clear above the tie bars K. The punch N and die 0 are remove able like the grippers P and G to adapt the machine for bending plates of different shapes. The attachment of the cylinders J to the ram makes a perfectly simple and very strong construction which works automatically to first clamp the blank and then draw it" while holding its ends with a substantially constant pressure sufiiciently moderated to prevent tearing the blank. The

grippers G are inclined on their ends and there is consequently a strong lateral force acting against the grippers and the blocks H. But these blocks bear inward against the punch N and are thereby absolutely held against yielding. The ends of the blank may be quitelon and weighty and the faces of the grippers 5 and P are inclined to give a substantial downward incline to the gripped ends of the blank, thus minimizing the difliculty of drawing them through the grippers. p

The blank Q being placed in the machine, its ends are grippedwith a determined pressure' atthe first upward movement of the punch. During the further movement of the punch the ends, though permitted to slip as sufficient with some shapes and metals.

grip'on the sheet even before the latter is pressed clear up to the die. To secure the general curves desired it is not necessary to press the sheet clear against thedie, the drawing of itover the punch alone being other cases it may be made to bear against the die'where the shape desired is diflicult to secure otherwise.- Or, as in thecase illus trated, the punch may be made tocarry the blank against the die throughout the-entire area of theblank, and such contact is necessary to form the sharply curved stiffening ribs of the plate shown in Figs. 1, 2 and 3.

After the drawing operation in-themachine illustrated,'the ends of the blank may be tensions B and end ribs O D and E may 1 be formed as shown, in dotted lines, in Figs. 2 and 3. v

Though I have describedwith great particularity of detail a specific machine embodying this invention, yet it is notto be understood therefrom thatthe invention is restricted to the particular machinedescribed. Various modifications thereof in detail and in the arrangement and combination of the parts may be made, and segregabl'e parts of the apparatus may be used in other connections, by those skilled in the art, without departure from the invention.

What I claim is .1. An apparatus for bending and drawing sheet metal to make parts of vehicle bodies or the like, which are curved in two planes transverse to each other, comprising grippers adapted to hold two opposite sides of the blank and to leave it free at the other two sides, a punch located between said grippers, said punch having its face curved both in planes parallel to the sides which areheld and in planes perpendicular thereto, and a die against which the intermediate part of the blank may be pressed by said punch, said die and punch being also formed with registering ribs and grooves respectively to form stiffening ribs on the blank.

2. An apparatus for bending and drawing sheet metal to make parts of vehicle bodies or the like, comprising an upper pair of grippers P and a lower pair of grippers G, said grippers adapted to hold two opposite sides of .the blankand having their faces inclined downward toward the outer side so as to provide for a downward incline of the extending ends of the blank, and means for bending and drawing the portion of the blank between the grippers atopposite sides.

3. Anapparatus for bending and drawing sheet metal, comprising grippers, a punch, and hydraulic devices carried by sa-id'pun'ch for pressing and holding said grippers into engagement with the work as the punch is advanced, said punch being adapted to engage and withdraw said grippers'near the end of its retractile movement.

4. An apparatus for bending and drawing sheet metal, comprising grippers G adapted to engage and bear against the work on'an angle tending to press said grippers inward, and a punch located between said grippers in position to resist the inward thrust-thereof.

5. An apparatus for bending and drawing sheet metal, comprising grippers adapted to yieldingly hold two opposite sides ofthe blank while leaving it free at the other two sides, and a punch located between said gripper-s, said punch having its face curved both in planes parallel to the sides which are gripped and in planes PQIPOIlCllCUlfTLl there to, and movable relatively to the grippers to a linal position projecting beyond them, the grippers adapted to hold the blank with sullicient force to draw the sheet metal into con "formity with the curved face of the punch while permitting the blank to tend between the gripping surfaces as it is drawn by the punch, such food being unequal at dill'erent points along the gripped sides of the blank.

(I. An apparatuslor bending and drawing sheet metal, comprising grippers adapted to hold two opposite sides of the blank and to leave it free at the other two sides, a punch located between said grippers, said punch having its :face curved both in planes parallel. to the sides which are held and in planes perpeinlicular thereto and movable relatively to the grippers to a final position beyond them, whereby in said position the distance from one gripper to the other following the face of the punch varies in dill'erent planes transverse to the grippers, and the grippers adapted to hold the blank yieldingly and lirmly enough to draw the metal against the contour of the punch during snchadvance movement while permitting the metal to lfeed between the gripping faces, such food being unequal at dill'ercnt points along the grippers.

7. An apparatus for bending and drawing sheet metal, comprising grippers adapted to yieldingly hold two opposite sides of the blank while leaving it free at the other two sides, and a punch located between said grippers, said punch having its face curved both in planes parallel to the sides which are gripped and in planes perpendicular thereto and movable relatively to the grippers to a final position projecting beyond them, the grippers adapted to hold the blank with sullieicnt lforce to draw the sheet metal into conformity with the curved face of the punch while permitting the blank to feed between the gripping surfaces as it is drawn b the punch, such feed being unequal at dillerent points along the gripped sides of the blank, and a die located adjacent to the linal position of the punch and conforming thereto, whereby the already conformed blank is finallysqucezcd between the punch and die.

In witness whereof, I have hereunto signed my name in the presence of two subscribing witnesses.

NORMAN A. ROBERTSON.

Thomas F. WALLACE, Fin-:1) il nrrn. 

